This invention lies in the field of cardiac pacers and more particularly, programmable atrio-ventricular pacers.
In the field of cardiac pacers, by far the dominant form of pacer is the demand ventricular pacer which provides stimulus pulses to a patient's ventricle in the absence of naturally occurring ventricular (QRS) heartbeats. A less frequently used type of pacer, although by now well known in the art, is the atrio-ventricular or sequential type of pacer which provides a first stimulus to the atrium to contract it and then a second stimulus to the ventricle, the second stimulus being delayed with respect to the atrial stimulus in accordance with the known A-V delay of a normal heart. In particular, this invention relates to a pacer having independent ventricular and atrial stimulating circuits which are both synchronized with respect to the activity of the patient's ventricle, i.e., the timing of the ventricular and atrial stimulus pulses is synchronized with the contraction of the ventricle, whether such contraction be naturally occurring or caused by the delivery of the ventricular stimulus pulse from the pacer itself.
Another feature that is currently gaining wider acceptance in the pacer area is that of programmed control of preselected pacer operating parameters. As is shown in the prior art, including U.S. Pat. No. 4,049,004, assigned to the same assignee, it is known that selected operating parameters may be controlled through program signals generated externally of the patient, transmitted to and received by the pacer implanted within the patient, and then transformed into appropriate control signals for control of the selected parameters. However, there remains a need for efficient utilization of such programmed control concepts in the embodiment of a programmable atrio-ventricular pacer, so that the advantages of programmable control may be extended to this more specialized form of pacer.